INTEGRATED WEED MANAGEMENT SYSTEMS FOR ORGANIC AND CONVENTIONAL CROPS OF THE SOUTHEASTERN COASTAL PLAIN
Location: Crop Protection and Management Research
Title: Benghal dayflower (Commelina benghalensis) seed viability in soil
Submitted to: Weed Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 11, 2012
Publication Date: N/A
Interpretive Summary: Benghal dayflower is one of the most troublesome weeds of cotton in the southeastern United States, and one of the first new weeds to appear in glyphosate-resistant cotton production. An exotic invasive species, Benghal dayflower is problematic in corn, cotton, and peanut in Georgia, Florida, and North Carolina. Benghal dayflower has a natural tolerance to many commonly used herbicides in agronomic crops, including glyphosate. In an effort to assist in the development of effective multiple-season Benghal dayflower management strategies, a greater understanding of the longevity of Benghal dayflower in the soil seedbank is needed. Seed longevity studies were conducted in Georgia, Florida, and North Carolina. In North Carolina, Benghal dayflower seed viability at the initiation of the study was 84%, declining to 81% after 6 months and 51% after 24 months of burial. By 36 months, seed viability was 27%, with viability less than 1% after 42 months. In Georgia, initial seed viability was 86%, declining to 63 and 33% at 12 and 24 months, respectively. Burial of 36 months or longer reduced seed viability to less than 2%. In Florida, seed viability at the first sampling date after two months of burial was 63%. After 34 months of burial, seed viability was reduced to 46% and then rapidly fell to 7% at 39 months, which was consistent with the findings of seed viability at the other locations. While physical dormancy is imposed by the seed coat of Benghal dayflower, decline in buried seed viability to less than 7 and 2% within 39 and 48 months suggests that the soil seedbank of Benghal dayflower is more ephemeral than persistent. Management programs in the southeast must prevent seed production for at least four growing seasons to reduce the soil seedbank population.
Benghal dayflower is a challenging weed to manage in agricultural settings. Research was conducted in North Carolina, Georgia, and Florida to evaluate the longevity of buried Benghal dayflower seeds. Seeds were buried for 2 to 60 months at a depth of 20 cm in mesh bags containing soil native to each area. In North Carolina, decline of Benghal dayflower seed viability was described by sigmoidal regression model, with seed size having no effect on viability. Seed viability at the initiation of the study was 81%. After burial, viability declined to 51% after 24 months, 27% after 36 months and less than 1% after 42 months. In Georgia initial seed viability averaged 86% and declined to 63 and 33% at 12 and 24 months, respectively. Burial of 36 months or longer reduced seed viability to less than 2%. The relationship between Benghal dayflower seed viability and burial time was described by a sigmoidal regression model. In Florida, there was greater variability in Benghal dayflower seed viability than at the other locations. Seed viability at the first sampling date after two months of burial was 63%. Though there were fluctuations over the first 24 months, the regression model indicated approximately 60% of seed remained viable. After 34 months of burial, seed viability was reduced to 46% and then rapidly fell to 7% at 39 months, which was consistent with the decrease in seed viability at the other locations. While there is a physical dormancy imposed by the seed coat of Benghal dayflower, it appears that a decline in buried seed viability to minimal levels occurs within 39 to 48 months in the southeastern U.S., suggesting that management programs must prevent seed production for at least four growing seasons to severely reduce the Benghal dayflower soil seedbank.